Tuesday

July 22, 2014

July 22, 2014

Posted by **sandy** on Monday, March 18, 2013 at 12:32am.

Sample 1: 11.6, 17.2, 15.0, 16.3, 22.9, 13.5, 16.4, 16.1

Below is a second random sample, independent from the first, of size 8 from a second normal population. Remembering that the F distribution is a ratio of independent chi- squares divided by their degrees of freedom, it can be shown that, under random, independent sampling, if the variances of the populations are equal, then s21/s2 has an F distribution with, in this case, 7 numerator and 7 denominator degrees of freedom (where the degrees of freedom are n − 1 for the corresponding samples). Test at α = .05 the null hypothesis that the variances are equal against the alternative that the variance of the first population is greater.

Sample 2: 17.7, 11.0, 17.0, 12.4, 10.8, 9.9, 17.2, 10.1

- statistics -
**MathGuru**, Monday, March 18, 2013 at 7:49pmFor your first problem:

Standard Deviation = 3.29 (Standard deviation is the square root of the variance)

Variance = 10.82 (Variance is standard deviation squared)

Using a chi-square table for the endpoints:

(n-1)s^2/16 to (n-1)s^2/1.69

(8-1)10.82/16 to (8-1)10.82/1.69

7(10.82)/16 to 7(10.82)/1.69

75.74/16 to 75.74/1.69

4.73 to 44.82 -->confidence interval for the variance

=================================

For the second problem:

Standard Deviation = 3.43

Variance = 11.76

Sample 1: n = 8; variance = 10.82; df = n - 1 = 7

Sample 2: n = 8; variance = 11.76; df = n - 1 = 7

Test statistic = sample 1 variance / sample 2 variance

You can use the F-distribution at .05 level using the above information for degrees of freedom. This will be your critical value to compare to the test statistic. If the test statistic exceeds the critical value from the table, the null will be rejected in favor of the alternative hypothesis. If the test statistic does not exceed the critical value from the table, then the null is not rejected.

I'll let you take it from here to finish. Check these calculations!

**Related Questions**

probability - Let X be a continuous random variable. We know that it takes ...

statistics - Suppose x has a normal distribution with mean μ = 35 and ...

Stor - Here is a simple way to create a random variable X that has mean μ ...

statistics - Suppose a random sample of size 50 is selected from a population ...

statistics - Suppose a random sample of size 50 is selected from a population ...

Quantum Physics - The variance σ2X=⟨(X^−⟨X^⟩)2&#...

Please help me - How many permutations σ of the set {1,2,…,15} are there ...

Physics - A spherical shell of radius R carries a uniform surface charge density...

Statistics - When testing H0: σ12 = σ22 vs. Ha: σ12 ≠ &#...

statistics - Statistical Abstracts (117th edition) reports sale price of ...